Electrochemical Generation of Individual O2 Nanobubbles via H2O2 Oxidation

Herein, we use Pt nanodisk electrodes (apparent radii from 4 to 80 nm) to investigate the nucleation of individual O-2 nanobubbles generated by electrooxidation of hydrogen peroxide (H2O2). A single bubble reproducibly nucleates when the dissolved O-2 concentration reaches similar to 0.17 M at the Pt electrode surface. This nucleation concentration is similar to 130 times higher than the equilibrium saturation concentration of O-2 and is independent of electrode size. Moreover, in acidic H2O2 solutions (1 M HClO4), in addition to producing an O-2 nanobubble through H2O2 oxidation at positive potentials, individual H-2 nanobubbles can also be generated at negative potentials. Alternating generation of single O-2 and H-2 bubbles within the same experiment allows direct comparison of the critical concentrations for nucleation of each nanobubble without knowing the precise size/geometry of the electrode or the exact viscosity/ temperature of the solution.